Various techniques have been developed for providing adjustment mechanisms for chair components such as chair backs or rests, arms, seats, among others. One common design of a vertical adjustment mechanism for a chair back includes a bar that extends upwardly from the chair seat. The bar fits into a sleeve attached to the backrest. The bar features a vertical slot defining a rack having a plurality of teeth. A pawl or pin secured to the sleeve is urged into engagement with the rack, for example by use of springs, and the boundaries of the teeth provide discrete positions of the backrest selectable by the user. To prevent dislocation of the springs, which can reduce the performance of the adjustment mechanism leading to failure, prior approaches have attempted to attach the springs to the sleeve through the use of covering plates, and to provide pockets or cavities within the sleeve for the (pre-tensioned) springs. It can be a challenge to shape the pockets correctly when fabricating sleeves in large quantities using an injection molding process. More generally, it is desirable to reduce the number of required parts and to extend the useful life of the springs and the reliability of the adjustment mechanism.
Improvements in linear adjustment mechanism are desirable, including those for chairs. For example, there is a need for the design and development of a linear adjustment mechanism that is reliable and secure, and simple and less costly to manufacture in scale and with fewer parts.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a review of the drawings.